Optimism is Good Medicine
Optimism affects how people react to stressful life events. Specifically, people who are more optimistic are at less risk for anxiety and depression after something stressful happens to them. Apparently, the kind of optimism that reduces the risk of depression is different than the kind that protects against anxiety. Specifically, having positive expectations for the future is what counteracts depression while a having a sense of being invulnerable is what lowers anxiety.